igoo-i.] 



Observations on Blood Pressure. 



191 



others. Thus, Tracing 4 is from a dog under morphia and chloroform 

 just as in the previous experiment, and yet the change in pressure in 

 the different postures is very shght. I found that cats are especially 



xuvu"iru^nnruinru\nm\ruAnnnnru\iu\runruuinnn^^ 



Tracing IV. — 9/22. — Dog: under Morphia and Chloroform. : Vertically teet downwards, 2 Hori- 

 zontal. 3 Head downwards. 4 Horizontal. 



immune to the effects of change of posture ; and Mr. Leonard Hill 

 records ^ that some animals, e.g:, certain species of monkeys, actually 

 (?z^^r-compensate, and thus have a higher carotid blood pressure in the 

 feet-down than in the normal posture. 



Most animals compensate somewhat after a short time for the 

 vertical feet-down position. As one might expect, animals that 

 habitually or frequently assume the vertical posture are better able to 

 compensate against any fall in blood pressure in this posture than are 

 animals which do not naturally become vertical. Thus apes and domestic 

 fowls compensate well, while snakes and hutch rabbits compensate 

 badly.'- 





if"^ 



i)>>.r'nvi^hT^''"''oi ''■''^v 



y 



Tracing V.— g/19. — i Vertically feet downwards. 2 Compensation occurring for vertical posture. 

 3 Horizontal again. 



Tracing 5 shows such compensation. At i the animal was placed 

 vertical, and at 2, though still in the vertical posture, the blood pressure 



1 " The Cerebral Circulation," page 88. 



2 Leonard Hill, " Further Observations on the Influence of Gravity on the Circulation," Supplement to 

 the Journal of Physiology, Vol. 23, Feb. 27th, 1899. 



